Infant skin barrier evaluation and nursing

Research on infant skin barriers has been one of the important topics shared by obstetricians and dermatologists. After the newborn is born, it is separated from the long-term amniotic fluid soaking, leaving the mother’s relatively stable temperature environment. The skin structure and function generally take 1 to 2 years to develop to the same level as adults, so the infant’s skin is very delicate, sensitive and susceptible. Stimulate and even infect. How to properly care for infant skin is an important topic, and understanding the infant’s skin barrier is an important prerequisite for the correct implementation of relevant care measures. The skin barrier function is mainly reflected in the superficial stratum corneum of the epidermis. Although the stratum corneum is only 7 ~ 35μm thick, it plays an important physical barrier function, such as regulating body temperature, gas exchange, moisture moisturizing, etc.; more and more research Both support keratinocytes are closely related to skin immune function. For example, a slight change in the pH of the skin surface can help the body to be protected from external pathogens, especially for babies. According to a recent study, the skin barrier function of infants is gradually improved within 5 years after birth, especially within 1 to 2 years, which is significantly related to the expansion rate of the infant’s epidermal area. An in-depth understanding of the skin barrier function has become an important part of basic research on infant skin.

1. Study on the structure, function and composition of infant skin
The relevant understanding of the infant’s skin barrier has been gradually improved during the gradual improvement of non-invasive skin detection methods and techniques. From the earliest invasive skin histology observation, to the skin B-ultrasound, and then to the skin confocal microscope, the researchers can see the infant’s skin development and development process from the cell level; the skin non-invasive detection method developed from the end of the last century, In addition to structurally, it is more functionally to visualize and digitize the evaluation of infant skin barrier function; currently some densitometry or spectrophotometry or electron microscopy (confocal Raman) can be used to correlate ingredients in infant skin. For example, natural moisturizing factors, ceramides, etc. are quantitatively determined.

1.1 Differences in skin structure between infants and adults

1.1.1 Epidermis
In the first year of life, the stratum corneum of the infant is nearly 30% thinner than the adult, and the basal layer of the epidermis is only 80% of the adult. The data confirmed that the thickness of the stratum corneum in the infant’s calf was 7.3±1.1μm, and the thickness of the same part of the adult reached 10.5±2.1μm. It was also found that the average number of newborn keratinocytes in the newborn was 4.3±0.7. The average number of cell layers in premature infants is 2.9 ± 0.5, so the temperature loss, may also lead to electrolyte changes in the body, hypernatremia or dehydration, so care should be paid to the care of premature infants. The thickness of the infant’s stratum corneum has changed significantly within 6 months of birth. There were studies using skin confocal microscopy to observe the skin stratum corneum of 15 Japanese newborns for 6 months. It was found that neonatal stratum corneum thickness was thinner at birth, 1 month and 3 months compared with their mothers. After the obvious thickening.
1.1.2 dermis
The infant’s dermis is relatively thin, and the true epidermis is flat and the associated fibers in the dermis are significantly smaller than adults. The connection between the dermis is not tight, and the skin barrier function may be damaged under friction and the skin integrity is lacking. The dermal microvascular structure was more obvious at birth, and then gradually subsided. By 3 months, it became a distinct dermal papilla structure, and the infant’s blood vessels were rich, so it looked rosy.
1.1.3 skin appendage
Infant hair development from the fetal hair to the mane, and then to the terminal hair, has its specific development process; sebaceous gland activity is more active in the mother, one month after birth has subsided, and is in a stationary phase within one year; infant sweat gland is structurally intact, However, there is often a lack of potent regulation of autonomic function; the nerves in the infant’s skin are small, and the myelinated nerve contains more axons than adults.

1.2 Differences in skin function between infants and adults
???With the development and renewal of skin non-invasive detection technology, researchers can more objective, specific, and digitalize the skin function of infants and adults. The most classic parameter is the transepidermal water loss rate (TEWL), which has been widely used in the evaluation of infant skin barrier function. This value is much higher in infant skin than in adults, but needs to be scientifically viewed and analyzed during different stages of growth and in different parts of the infant. Some studies have shown that the water content of the stratum corneum of infants is more than that of adults; there are also tests for dynamic observation. The infant’s moisture content is low within 1 to 15 days after birth, and will increase to 6 months, and then decrease to the same level as adults. However, most of the data support the absorption and loss of skin moisture in infants, which is higher than that of adults. The skin’s stratum corneum moisture “gets fast and out fast” is one of the important characteristics of infant skin barrier. The moisture in the infant’s skin stratum corneum is too fast. One of the important reasons for the temporary imperfection of the infant’s skin barrier. Therefore, for infant skin care products, it is also necessary to be cautious. The substances applied to the infant’s skin may be more easily absorbed by the epidermis, and the chance of irritation or allergic reaction is higher. At present, the evaluation of the safety of products used in infants is often carried out by applying a repeated challenge patch test and a cumulative stimulus patch test.
???The pH of the infant’s skin surface is also very different from that of adults. In healthy adults, the pH of the skin is <5, which is weakly acidic; while the pH of the infant’s skin is 5.4 to 5.9. The weak acidity of the skin is one of the important barriers to maintain the skin against external aggressions. On the basis of high moisture content of the infant’s skin, if there is further stimulation of urine or sweat, the local pH value of the skin is further increased, which is one of the important reasons for diaper dermatitis or other skin diseases.

1.3 Differences in skin composition between infants and adults
In the differences in skin composition between infants and adults, many studies have focused on the study of sebum, natural moisturizing factors and ceramides.
1.3.1 Determination of infant sebum
Sebum testers or densitometry or spectrophotometry have shown that sebum is the same as that of adults at birth, but sebum will gradually decrease. Such a dynamic change in sebum content also explains many clinical phenomena, such as infantile seborrheic dermatitis, which usually occurs in newly born babies.
1.3.2 Detection of natural moisturizing factors in infants
Many studies use an electron microscope (confocal Raman method) to detect natural moisturizing factors in infants. When the infant is born, the natural moisturizing factor is higher than that of the adult, which is reduced to 6 months and lower than that of the adult. It is not equivalent to the adult level until after 1 to 2 years old.
1.3.3 Determination of ceramide
The ceramide measurement is a research hotspot for evaluating the skin barrier of infants, but the results of different experiments are also different. Early studies have shown that the amount of epidermal ceramide is the same as that of the 20- to 28-week fetus at 6 weeks after birth, but the epidermal ceramide in the same site is lower than that of the adult. Subsequent studies compared ceramide in different parts of the infant. The ceramide in the infant’s thigh was lower than that in the adult, but the abdomen was higher than the adult, while the waist and hip were the same as the adult. Therefore, the difference in the amount of ceramide in different parts was considered to be different from that in adults. There are significant differences. There is also a recent study on ceramides during infancy
Dynamic observations were made: higher than adults at birth, but gradually reduced, and comparable to adult levels at 12 months.
Therefore, whether it is sebum, natural moisturizing factor, or ceramide, most studies have confirmed that infant skin related components are significantly different from adults, and are in the process of continuous improvement and growth in the infant stage.

2. Common evaluation methods for infant skin barrier
The application of non-invasive skin detection technology to the repeated measurement and evaluation of infant skin not only provides researchers with further understanding of the infant skin development process, but also provides an important basis for the evaluation of the efficacy and safety of infant products.

2.1 Determination of skin water loss rate
TewameterTM 210 (Courage + Khazaka-electronic GmbH, Germany) is one of the commonly used skin non-invasive instruments commonly used for the detection and evaluation of skin barrier functions based on Fick’s law of diffusion. Assessing the amount of moisture lost in the skin per unit time is an important parameter of the barrier function. The higher the value, the worse the barrier function. The transepidermal water loss rate of most parts of the infant is higher than that of adults.

2.2 Determination of water content in the stratum corneum
Corneometer CM825 (Courage + Khazaka-electronic Gmb H) is an instrument based on the principle of capacitance to measure the water content of the stratum corneum of the skin. It is also one of the important parameters for the evaluation of skin barrier function. The higher the value, the more water content in the stratum corneum. The water content of the stratum corneum in most parts of the infant is higher than that of adults.

2.3 Skin surface p H value determination
SKIN-p H-METER PH /905 (Courage +Khazakaelectronic Gmb H in Germany) measures the concentration of hydrogen ions or hydroxide ions by measuring the difference in surface potential of the skin to determine the pH of the skin surface. The surface pH of infant skin is often higher than that of adults, and it is alkaline, so the skin barrier function is relatively weak.

2.4 Determination of sebum
Sebumeter SM815 (Courage + Khazakaelec-tronic Gmb H) is based on the principle of a special tape photometer. After the matt tape absorbs the oil on the skin, it gradually becomes transparent, and its light transmission amount also changes. The more oil is absorbed. The greater the amount of light transmission. The skin surface fat content is indirectly measured by such a principle. The surface of the infant’s skin has a dynamic process within one year after birth.

2.5 skin B-ultrasound or electron microscope
Commonly used is the UC22 skin ultrasound system (Courage+ Khazakaelectronic Gmb H). With a center frequency of 22MHz and a depth of 6 to 8mm, the B-ultrasound can penetrate the dermis to part of the subcutaneous tissue and provide up to 33μm lateral resolution, clearly showing the structure of the skin and its pathological changes. For determining the thickness or density of the infant’s epidermis,
The thickness or density of the dermis allows for repeated quantitative detection.
Recently, there have been studies using electron microscopy (confocal Raman) parameters to describe the micromorphological changes in the surface of the infant’s skin, which can semi-quantitatively describe the maturity of the infant’s skin. For example, the semi-quantitative index of the uniformity evaluation under the electron microscope and the degree of decomposition of keratinocytes can be used as an important evaluation index for the cell maturity of infant skin.

2.6 skin confocal microscope
The skin confocal laser scanning system Vivascope1500 (Lucid, USA) is a new method in the non-invasive detection of skin. From the histological point of view, the microstructure of the skin is 350μm. Although the depth has obvious limitations, it is used to evaluate the skin barrier function of the infant. ,very meaningful. It can qualitatively and quantitatively observe all levels of the skin, not only to observe the subtle changes of cells or blood vessels or fibers, but also to make a lot of refinement for quantitative detection. Therefore, it provides a number of relevant parameters for the study of infant skin barrier function.
For the clinical application of non-invasive detection technology for infant skin barrier, it is necessary to carry out different methodological (at least 3) combinations according to actual needs, in order to be relatively objective and comprehensive evaluation (the relevant method and technology are summarized in Figure 1). For the evaluation of the skin barrier in children with atopic dermatitis, the skin water loss rate and skin water content are often used to evaluate the physiological state of the skin, and at the same time combined with some related skin imaging techniques, such as skin B ultrasound or skin confocal microscopy. Perform structural analysis and measurement at different levels.

3. infant skin barrier care guidelines

The fundamental purpose of understanding the infant’s skin barrier is to better care for the infant’s skin, especially if they are still not mature within 1 to 2 years of birth. In China, the “China Maternal and Child Health Association” has jointly developed the “Guidelines for Newborn Skin Care” jointly with renowned obstetrics and gynaecology and dermatologists, and has been updated to the second edition, which is of great significance for the scientific promotion of infant skin care. . The European “Healthy infant Skin Care Roundtable” organized a guide on infant skin cleansing and bathing in 2009; in 2016, they again updated guidelines for infant skin moisturization and diaper rash prevention. In combination with China’s national conditions, there are also related principles for infant skin barrier care.

3.1 Choosing the right shower gel can improve the infant’s skin hygiene
Detergents cleanse the skin’s sweat, oils, metabolites, etc., but they can also cause dryness, tightness, or scaling. Compared with soap, liquid cleansers – shower gels are relatively milder and more suitable for long-term use on infant skin.
For the skin barrier characteristics of infants, it is recommended to choose a mild liquid bath with a neutral or weak acid pH of 5.5-7.0, which has less effect on the skin surface p H value; at the same time, try to avoid the use of antibacterial soap, related to antibacterial soap Ingredients may have an effect on the colonization of the infant’s skin surface, and may further damage the otherwise unsound infant skin barrier; in addition, try to avoid infant bath products containing potentially high-sensitizing flavors or preservatives. Preservatives or flavors and fragrances are important ingredients in bath products or cosmetics, but because infant skin barriers are relatively weak, it is not recommended to add such highly sensitizing ingredients to infant shower gels.

3.2 Choose a suitable lotion to enhance the infant’s skin barrier function
The infant’s skin barrier is fragile, and the rate of water loss through the epidermis is high, which is prone to dryness and desquamation. It is prone to irritation or allergic reaction after using the product. Therefore, the selection of a suitable lotion is necessary to enhance the infant’s skin barrier function. The principle is the same as the choice of shower gel. The first is to choose a non-irritating lotion that can change the surface condition of the infant’s skin, so that the infant’s skin barrier can be improved. If some skin care products contain natural moisturizing factors or ceramides, this is more suitable and safe for infant skin. Secondly, try to avoid using emollients with high sensitizing ingredients, because the emollient will reside on the skin. For a certain period of time, the requirements for irritating and sensitizing ingredients may be higher; finally, pay attention to the timing of using emollient, use within 5 minutes after the infant is bathed and dry, can better combine the hydration of the skin, will The moisturizing effect of infant skin has been improved.

3.3 Scientific nursing of infants can effectively reduce the incidence of diaper dermatitis
The relevant components in urine or feces can cause the pH of the infant’s skin surface to rise from 5.5 to 6.8 to 7.15, causing great damage to the skin. At the same time, the humidity in the environment of the urine layout is increased due to urine, plus the activity of the infant. Rubbing the skin with the diaper will further damage the skin barrier function of the infant. On the basis of the skin barrier that is not perfect, the chance of diaper dermatitis is very high. According to UK study data, the incidence of diaper dermatitis in infants is 25% within 4 weeks of birth and the highest incidence in infants between 9 and 12 months. However, for this kind of irritating diaper dermatitis, direct scientific care of local skin can effectively reduce the incidence of diaper dermatitis.
Therefore, it is recommended to choose a diaper with good permeability, try to achieve the same humidity and temperature inside and outside the diaper; the diaper material should have good absorption performance, so that the infant will not have obvious sultry and moist feeling; the material not only has good absorption performance, but also needs to be as soft as possible. Reduce friction and damage; diaper design should be close to the body, but not tight, easy to explore the infant’s activities.

After more than ten years of non-invasive detection of skin and related research on the skin barrier of infants, dermatologists have become clearer: infant skin is in a phase of perfection within 1 to 2 years after birth. For this special period of skin care, more attention needs to be paid. The understanding of the infant’s skin barrier will continue to deepen in the future practice. On the one hand, it relies on the renewal and development of skin bio-detection technology, and also relies on the further development of the science of cosmetic raw materials to help infants filter out safer and more effective related ingredients.